Hand-held vacuum pump and automated urinary drainage system using pump thereof

ABSTRACT

In the hand-held vacuum pump  1,  the main body  1   a  of the vacuum pump in which the pump room  4   a  is formed and the electric motor  2  are connected via the shaft coupling  21.  The main body of the vacuum pump has the driving shaft  10.  One ball bearing  15   b  supporting the driving shaft is supported by the cylinder. The other ball bearing  15   a  is sup ported by the flange  5  mounted hermetically at the cylinder. The end part of the cylinder at the side of the electric motor accommodates the shaft coupling, and is engaged with the end part of the electric motor so that the electric motor may support the cylinder.

BACKGROUND OF THE INVENTION

The present invention relates to a hand-held vacuum pump, andspecifically to a hand-held vacuum pump preferable for an automatedurinary drainage system.

An example of the urine suction apparatus for urinary drainage for thepeople finding difficulty in moving on his or her own ability to theplace where he or she relieve himself or herself is described in theJapanese Patent Application Laid-Open No. 2003-126242. In the urinesuction apparatus sited in this Patent Gazette, a urine storagecontainer is located between the urine receiver and the suction pumpoperated as the suction engine. When the urine is discharged into theurine receiver, the urine discharge is detected and the discharged urineis sucked from the suction pipeline into the urine storage container. Inthis operation, the suction operation of the suction pump is controlledby referring to the signal from the pressure sensor for detecting thechanges in the pressure inside the urine storage container.

A lightweight vacuum pump is used generally for the suction pump. Anexample of this type of vacuum pump is described in the Japanese PatentApplication Laid-Open No. 2002-195180 and the Japanese PatentApplication Laid-Open No. 8-296575. In the compressor described in theJapanese Patent Application Laid-Open No. 2002-195180, in order toimprove the sliding characteristic and ultimately the efficiency, such asliding member as providing a continuous lubrication function by meansof self-lubricating operation is provided at the rotary compressor. Incontrast, in the movable vane compressor and vacuum pump described inthe Japanese Patent Application Laid-Open No. 8-296575, the compressorroom and the pump room for the sealing fluid are partitioned separatelyand hermetically, and the sealing fluid discharged out from the pumproom is supplied to the sealing part and the lubricating part.

In the conventional urine suction apparatus sited in the Japanese PatentApplication Laid-Open No. 2003-126242, what is disclosed is that theoperation state of the suction pump operated as suction engine ischanged in response to the pressure inside the urine storage container.However, in the Japanese Patent Application Laid-Open No. 2003-126242,there is not sufficient consideration for downsizing the suction pumpand reducing its operation noise. In case of downsizing the overallsystem in order to increase the portability of the urine suctionapparatus, it is required to downsize the suction pump itself. Althoughone of the most effective methods for downsizing the pump is to increasethe rotating speed of the pump, in case of attempting to increase therotating speed of the pump, especially the positive displacement pumpgenerally used as the small-sized pump, the relative gap between therotating member and the stationary member increases which leads toreducing the efficiency. In addition, increasing the rotating speedsimply may result in the increase in the noise generated from the pump.As for the urine suction apparatus, the usage out of doors as well asthe usage bedside especially in the night should be considered, whichrequires inevitably the reduction of the noise.

In contrast, in the compressor sited in the Japanese Patent ApplicationLaid-Open No. 2003-126242 and Japanese Patent Application Laid-Open No.8-296575, the reliability of the sealing part and the lubricating partis increased in order to prevent the reduction in efficiency due to thedownsizing of the overall system. However, as this compressor is notintended to be used for the hand-held medical device such as urinarydrainage system, the downsizing of the compressor may experience acomplexity in the structure of the compressor itself that is the resultof the design respecting the performance primarily. In addition, theintended use of the compressor does not assume the usage in the night,and thus, there is not sufficient consideration of the reduction of thenoise generated in the intermittent operation of the compressor.

BRIEF SUMMARY OF THE INVENTION

In order to solve the problems in the prior art, an object of thepresent invention is to downsize the vacuum pump and increase itsportability. Another object of the present invention is to increase thereliability of the vacuum pump having portability. Further anotherobject of the present invention is to enable the urinary drainage systemhaving a vacuum pump to be used in the night and out of doors.

The characterized feature of the present invention to achieve the aboveobject is that, in the hand-held vacuum pump in which the electric motorand the main body of the vacuum pump are connected through the shaftcoupling, one bearing supporting the driving shaft included in the mainbody of the vacuum pump is supported by the cylinder and the otherbearing is supported by the flange mounted hermetically at the cylinder,and the end part of the cylinder near the electric motor accommodatesthe shaft coupling and is engaged with the end part of the electricmotor, and the electric motor supports the cylinder.

In the characterized feature described above, the round hole to beengaged with the rotating shaft of the electric motor is formed at oneside of the shaft coupling and the quasi-square hole to be engaged withthe driving shaft passing through inside the cylinder is formed at theother side of the shaft coupling, and the hole to be engaged with therotating shaft of the electric motor is formed at the driving shaft,which may eliminates preferably the locking screw for fixing the shaftcoupling and the rotating shaft of the electric motor. In addition, itis preferable that the material of the shaft coupling is made to beresin, and plural protruding parts extending in the axial direction onthe inside face of the round hole formed at the shaft coupling areformed, or that plural holes extending in the radial directioncommunicating with this round hole are formed.

In the characterized feature described above, it is preferable that acouple of sliding cylinders having a circular arc part and clamping bothsides of the intermediate part of the extension part configured as aplate structure is provided, and this sliding cylinder is supported bythe cylinder and the sliding cylinder is made oscillating inside thecylinder, and the cylinder and the piston are formed as doublecylinders, and that the pump room is formed so that the shape of thepump room may change between the double cylinders.

In the characterized feature described above, it is preferable that thepiston is mounted at the driving shaft through the eccentric shaft, thispiston has a blade part configured as a plate structure extendingtowards the outer side at a part of its periphery, the sliding cylinderhaving a circular arc part supports this blade part so as to freelyoscillate, and that the material of the driving shaft is made to bestainless steel, the material of the shaft coupling is made to be PCresin or POM resin, the material of the piston is made to be PS resin orPC resin, the material of the cylinder is made to be PBT resin, and thematerial of the sliding cylinder is made to be PPS resin or PBT resin.Note that PC stands for Polycarbonade, POM stands for Polyacetal, PSstands for Polystyrene, PPS stands for Polyphenylene Sulfide, and PBTstands for Polybutylene Terphthalate.

In addition, in the characterized feature described above, it ispreferable that the balance weight is mounted at the end part of thedriving shaft for compensating the eccentricity between the piston andthe eccentric shaft, and the cover for covering the balance weight ismounted at the flange, and the material of the flange is made to be POMresin, and the cylinder and the piston are formed as double cylinders,and that the gas inside the pump room is compressed by changing thevolume of the pump room formed between the double cylinders byoscillating the blade part.

In addition, in the characterized feature described above, it ispreferable that the beveled cut part having a cross-sectional shape ofshaft shaped in D-sigmoid is formed at the driving shaft, and the holecorresponding to this D-sigmoid shape is formed at the eccentric shaft,and plural protruding parts extending in the axial direction are formedinside the hole shaped in D-sigmoid formed at the eccentric shaft, andthat the support part supporting the sliding cylinder is formed at thecylinder, and the suction passage for sucking the gas into the cylinderand the discharge passage for discharging the gas are mounted near thissupport part and the double cylinder part so as to be almost vertical tothe vibrating blade part, and a valve configured in a sheet structurefor opening and closing the discharge passage and a discharge valvepresser for pressing down this valve are provided at the dischargepassage. In addition, it is preferable that the diameter of the hand-held vacuum pump is 30 mm or shorter, its length is 70 mm or shorter,and its weight is 250 g or lighter, and the electric motor is driven bythe dry cell or the secondary battery providing an output voltagebetween 4V and 9V, and that the overall exhaust velocity when driven bythis vacuum pump at 4000 to 6000 rpm is about 80 mL/sec.

In another characterized feature of the present invention, the automatedurinary drainage system includes the hand-held vacuum pump having eitherone of the characterized aspects described above which provides theexhaust speed around 80 mL/sec and the weight of 250 g or lighter.

According to the present invention, as the structure of the vacuum pumpis simplified, it will be appreciated that the downsizing of the vacuumcan be attained and the portability can be increased. As the positioningaccuracy at the individual parts is increased by using a simplifiedstructure and the lubrication between the stationary parts and themoving parts are sufficiently provided, it will be appreciated that thereliability of the vacuum pump having portability can be increased. Asthe positioning accuracy is increased, it will be appreciated that thenumber of noise generation sources and their noise intensity can bereduced, and the urinary drainage system to which this vacuum pump isapplied can be used in the night and/or out of doors.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a side cross-section view of one embodiment of the hand-heldvacuum pump of the present invention.

FIG. 2 is an A-A cross-section view of FIG. 1.

FIG. 3 is a perspective exploded view of the rotor part of the vacuumpump shown in FIG. 1.

FIG. 4 is a perspective exploded view of the shaft coupling of thevacuum pump shown in FIG. 1.

FIG. 5 is a perspective exploded view of the driving shaft part used forthe vacuum pump shown in FIG. 1.

FIG. 6 is a side view of the shaft coupling used for the vacuum pumpshown in FIG. 1.

FIG. 7 is a perspective exploded view of another embodiment of the shaftcoupling used for the vacuum pump shown in FIG. 1.

FIG. 8 is a side view of the end part of the driving shaft used for thevacuum pump shown in FIG. 1.

FIG. 9 is a front view and a side view of the discharge valve stopper 19used for the vacuum pump shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Now referring to the attached figures, one embodiment of the hand-heldvacuum pump according to the present invention will be described. Thevacuum pump in this embodiment is mainly used for the urinary drainagesystem. FIG. 1 is a vertical cross section view of the vacuum pump, andFIG. 2 is an A-A cross-section view of FIG. 1. FIG. 3 is an exploded andperspective view of the main part of the vacuum pump shown in FIG. 1 andits B-B cross-section view, and FIG. 4 is an exploded and perspectiveview of the end part of the shaft of the vacuum pump shown in FIG. 1,and FIG. 5 is an exploded and perspective view of the shaft of thevacuum pump shown in FIG. 1.

In the hand-held vacuum pump 1, the main body 1 a of the vacuum pump isconnected to one side of the driving motor 2 through the shaft coupling21. The motor 2 drives the vacuum pump 1 at the rotating speed between4000 rpm and 7000 rmp. The diameter of the motor 2 is about 30 mm, andits axial length is about 35 mm. The motor 2 is driven by the dry cellor the secondary battery providing the voltage between 4V and 9V.

The intermediate part in the axial direction of the driving shaft 10connected to the motor shaft 2 a through the shaft coupling 21 isengaged to the hole formed at the eccentric position inside thecylindrical eccentric shaft 11, and the eccentric shaft 11 is drivenaround the eccentric axis around the motor shaft 2 a. The needle bearing12 is engaged at the periphery of the eccentric shaft 11. Both right andleft ends in the axial direction of the eccentric shaft 11 are supportedby the ball bearings 15 a and 15 b so as to rotate freely. The balanceweight 13 is mounted at the contact face 10 f of the eccentric shaft 11at the opposite side of the motor, that is, the left end part shown i nFIG. 1, on the basis of the contact face of the balance weight. Thebalance weight 13 is supported at the eccentric shaft 11 by the stopper14.

In order to prevent the lubricant which is coated at the ball bearing 15a supported at the ball bearing supporting part 5 a shaped in acylinder, but is not shown in the figure, from flying in all directions,the lubricant reservoir dish 5 b shaped in a cone is mounted around theball bearing supporting part 5 a. In case of installing the needlebearing 12 between the piston 3 and the eccentric shaft 11, the needlebearing fixing part 11 d for supporting the needle bearing 12 is formedby pressing the inner ring of the needle bearing 12 in the axialdirection.

The part of the driving shaft 10 on the side of the balance weight 13 iscovered by the cover 6 engaged with the flange 5. The fixing plate 4 dfor fixing the vacuum pump 1 at the urinary drainage system is providedon one side 4 c of the cylinder 4. In addition, the end part of thecylinder 4 on the side of the motor 2 is shaped in a cylinder, andaccommodates the shaft coupling 21 and is engaged with the engage partformed at the electric motor 2. Owing to this structure, the cylinder 4can be directly supported by the motor 2. The outer part of the cylindercorresponding to the pump room 4 a is formed as a double structure, andthe motor base 20 for supporting the periphery of the motor 2 is mountedat the end part of this double structure on the side of motor 2. Thus,the cylinder 4 is supported by the motor 2 also with the motor base 20.

The ball bearing 15 b is supported at the cylinder 4 integrated with thecasing which is a container shaped like a “Snowman” and has an openstructure at the left side shown in FIG. 1. On the other hand, the leftside ball bearing 15 a is supported by the ball bearing supporting part5 a formed at the flange 5. The flange 5 is a member configured at thein a plate structure covering the open face of the cylinder 4, and thededicated sheet 17 is arranged between the flange and the cylinder so asto be engaged hermetically with the cylinder 4. The dedicated sheet 17is a sheet composed of PTFE, and used for compensating the molding errorand the assembling error of the cylinder 4 composed of a resin material,the eccentric shaft 11, the piston 3 and the sliding cylinders 7 a and 7b, which will be described in detail below.

As the cylinder 4 slides on the dedicated sheet 17, the dedicated sheetis composed of easy-to-slide material. The dedicated sheet 17 can changeits shape when sliding with the cylinder 4. The piston 3 is mounted atthe periphery of the needle bearing 12, and this piston 3 have a ringand a blade 3 a formed by extending one part on the circumferentialdirection of this ring toward the outer side. The eccentric shaft 11,the needle bearing 12 and the piston 3 are accommodated inside thecylinder 4.

The intermediate part of the blade 3 a is clamped at the left and rightsides by the sliding cylinders 7 a and 7 b forming a part of thecylinder. The sliding cylinders 7 a and 7 b are supported by theprotruding part of the cylinder 4 with its inner surface shaped so as tobe fit to the external shape of the sliding cylinders 7 a and 7 b. Thehead part of the blade 3 a extends towards the space shaped in aelliptic cylinder formed at the inner face of the protruding part of thecylinder 4. The lower part of the piston 3 is shaped in a cylinder, andits peripheral surface 3 b faces to the inner surface 4 a of the lowerpart of the cylinder 4 shaped in a cylinder. The gap between the piston3 and the cylinder 4 establishes a very little clearance in order tokeep the sealing performance even at the narrowest gap. The piston 3 hasa swirling motion inside the cylinder 4. When the piston 3 swirls with aconstant radius, the bicephalic space 4 b formed between the innersurface 4 a of the cylinder 4 and the piston 3 moves by following tothis swirling motion. Then, the gaseous component is taken in from theintake passage 8 and discharged to the discharge passage 9.

The intake passage 8 and the discharge passage 9 are formed in thevertical direction orthogonal to the driving shaft 4 near the supportingpart of the cylinder 4 for supporting the sliding cylinders 7 a and 7 b.The intake passage 8 and the discharge passage 9 are open to the pumproom 4 b. The valve seat 9 b is formed at the discharge passage 9, andthe discharge valve 9 a contacts to this valve seat 9 b. The dischargevalve 9 a is a silicon sheet having a thickness of 0.5 mm. The dischargevalve stopper 19 presses down the discharge valve 9 a towards theopposite direction of the discharge flow. The discharge valve 9 a to bemounted at the discharge passage 9 is mounted at the location that ispossibly located on the internal surface 4 a of the cylinder and nearthe blade 3 a in order to reduce the dead volume. In this embodiment,the valve seat 9 b is formed by forming a hole larger than the diameterof the discharge passage 9 on the side of cylinder side face at thedischarge passage.

The detail structure of the discharge valve stopper 19 is shown in FIG.9. FIG. 9(a) shows the front view, and FIG. 9(b) shows the side view.The discharge valve stopper 19 is formed by processing and forming around-bar material. A through-hole 19 y is formed at the center part ofthe round bar, and a stepped shape having the step size 19 d equivalentto the discharge valve stroke in the axial direction is formed at itsback face. As shown in FIG. 9, a part of the step has a canted part. Theslotted part 19 j, which is a groove developed in the radial direction,is formed at the front side of the round bar, and the round hole 19 xlarger than the diameter of the through hole 19 y is formed up to theintermediate part in the axial direction. The hexagon hole 19 i isformed at the backside of the round hole 19 x, which is used formounting the discharge vale stopper 19 by using the hexagonal wrench.The diameter 19 a of the discharge valve stopper 19 is 5.0 mm.

The discharge valve 9 a having the diameter almost identical to thediameter of the discharge valve stopper 19 is arranged at the backsideof the discharge valve stopper 19. The discharge valve 9 a is a circularplate made of PTFE with 0.1 mm thickness, and its top part to thestepped part are pressed down by the discharge valve stopper 19 inaccordance with the shape of the discharge valve stopper 19. Thus, thedischarge valve can bend right and left at its stepped part to its lowerpart due to the pressure inside the discharge passage 9. The valvestopper length 19 b, measured from the top part to the stepped part, is1.15 mm. The valve aperture angle 19 c, which is the canted angle of thestepped part, is 45 degrees. The discharge valve 9 a bends with thesupporting points at the valve aperture supporting parts 19 e and 19 f,which are located at the both ends of the canted parts. As the lower endpart of the discharge valve 9 a can bend with the supporting point atthe valve aperture supporting part 19 f, the communication channelbetween the front side of the discharge valve stopper 19 and thebackside of the discharge valve 9 a can be established when thedischarge valve 9 a bends.

As the height of the air discharge port 19 h is established the innerside of the thick part 19 g of the ring formed by the penetration hole19 y formed at the discharge valve stopper 19, the channel communicatingfrom the penetration hole 19 y to the slotted part 19 j of the groovewidth 19K is formed. Owing to this structure, the discharge valve can beoperated definitely independently of the installation state of thevacuum pump. Note that the noise generated by opening and closing thedischarge valve 9 a can be reduced because the stepped part is formed asa canted shape.

As shown in detail in FIG. 4, the driving shaft 10 and the rotatingshaft 2 a of the motor 2 are linked together with the shaft coupling 21.The shaft coupling 21 is shaped in a cylinder, and has a round hole 21 aformed at the side where the rotating shaft 2 a of the motor 2 isengaged with the shaft coupling. On the other hand, a quasi-rectangularhole (square hole) 21 b which is formed by cutting a circle with acouple of lines is formed at the side where the driving shaft 10 isengaged with the shaft coupling. A fillet having a couple of planes 10 band 10 c parallel to each other is formed at the driving shaft 10corresponding to this square hole. A round hole 10 a with which therotating shaft of the motor can be engaged is formed at the center partof the driving shaft 10.

In the vacuum pump 1 so configured as described above, the flange 5 andthe dedicated sheet 17 are hermetically mounted at the cylinder 4, andthen the pump room 4 b is formed. The protruding part 4 e is formed onthe surface of the cylinder facing to the flange 5, and this protrudingpart is transformed when installing the flange 5 at the cylinder 4, andthus, the protruding part 4 e and the dedicated sheet 17 firmly contactto the flange 5. Owing to this structure, the sealing performance of thepump room 4 b is established.

When the motor shaft 2 a rotates, the eccentric shaft 11 rotates in aneccentric motion, and then the piston 3 mounted at the peripheral sideof the eccentric shaft also rotates in an eccentric motion. In thisoperation, the movement of the blade 3 a of the piston 3 is limited bythe sliding cylinders 7 a and 7 b, and then the rotation of the piston 3on its own axis is blocked. The material and shape (as a part of thecylinder) of the sliding cylinders 7 a and 7 b blocking the rotation ofthe blade 3 a on its own axis is selected to be appropriate for slidingperformance in order to make the movement of the blade 3 a smooth.

In this embodiment, the rotation driving power of the motor 2 istransmitted to the driving shaft 10 by using the static frictiongenerated between the rotating shaft 2 a of the motor and the round hole21 a. When the shaft coupling 21 rotates, the turning force istransmitted from the square hole 21 b formed at the shaft coupling 21 tothe flat surfaces 10 b and 10 c of the fillet of the driving shaft 10,and thus the driving shaft 10 rotates. Though the shaft coupling 21 wasfixed at the shaft 10 by using the clamp screw in the prior art, thisembodiment does not use the clam screw. The reason is that theapplication of the clamp screw makes the weight of the clamp screwitself operate as unbalanced load that may result in an occurrence ofvibration. As this embodiment does not use the clamp screw, it will beappreciated that the driving shaft 10 and the shaft coupling 21 can beengaged firmly. In addition, in view of the disassembly operation forthe driving shaft 10 and the shaft coupling 21, PC (Polycarbonate) resinis used for the material of the shaft coupling 21, which is aimed forweight saving and abrasion resistance.

Though this embodiment uses the shaft coupling 21 made of Polycarbonatefor the reason described above, it is difficult for the shaft coupling21 made of the resin material to establish the same level of moldingaccuracy as the metallic shaft coupling. In order to prevent the axialalignment deviation between the rotating shaft 2 a of the motor 2 andthe driving shaft 10 due to the molding error, this embodiment uses sucha structure that the rotating shaft 2 a of the motor 2 can be insertedinto the round hole 10 a. Owing to this structure, the vibration at thehigh-speed rotation which may result from the slight deviation in theaxial alignment between the rotating shaft 2 a of the motor 2 and thedriving shaft 10 can be reduced as well as the mechanical loss can beprevented. In addition, the axial length of the vacuum pump 1 can bereduced, which contributes to the downsizing of the vacuum pump 1.

This embodiment uses such a structure that the shaft coupling 21 is notfixed at the rotating shaft 2 a of the motor 2 by using the clamp screwand can be dismounted from the motor 2 without using the clamp screw. Inthe structure of this embodiment, the protruding part 21 c extending inthe axial direction shown in detail in FIG. 6 is formed on the innersurface of the round hole 21 a of the shaft coupling 21. Pluralprotruding parts 21 c are formed with an interval in the circumferentialdirection on the inner surface of the shaft coupling 21 c. FIG. 6(a)shows the side view of the shaft coupling 21 c alone, and FIG. 6(b) is across-section view of the structure in which the shaft coupling 21 ismounted at the rotating shaft 2 a of the motor 2. As the rotating shaft2 a is inserted into the shaft coupling 21, the protruding parts 21 c ofthe shaft coupling 21 made of the resin material are deformedelastically.

As plural protruding parts 21 c are formed on the inner surface of theshaft coupling 21, the rotation torque generated by the rotating shaft 2a of the motor 2 can be transmitted definitely to the shaft coupling 21owing to the friction force. In addition, owing to the deformation ofthe protruding parts 21 c, the accuracy of positioning, that is, axialalignment of the rotating shaft 2 a of the motor 2 can be established.Owing to the deformation of the protruding parts 21 c, the touch areabetween the rotating shaft 2 a of the motor 2 and the shaft couplingrequired for transmitting the torque can be ensured. The height of theindividual protruding part 21 c is determined so that the gap betweenthe protruding part 21 c and the rotating shaft 2 a engaged to eachother may not be developed when inserting the rotating shaft 2 a of themotor 2. Thus, even if the finished size of the round hole 21 a is alittle consistently different from the designed value or its finishingaccuracy has a little deviation, and even if the difference between thematerial of the rotating shaft 2 a and the material of the shaftcoupling 21 may result in the difference in their heat deformation,there is no gap between the protruding parts 21 c and the rotating shaft2 a, and hence, the rotation torque can be definitely transmitted.

The rotation torque is transmitted from the side surface of the squarehole 21 b of the shaft coupling 21 and the flat surfaces 10 b and 10 cof the fillet of the driving shaft 10 to the driving shaft 10. Thesquare hole 21 b and the fillet are used not only for transmitting thetorque but also for positioning the parts when assembling the parts. Byaligning the flat surfaces 10 b and 10 c of the fillet onto the two sidesurfaces of the square hole 21 b, the shaft coupling 21 can bepositioned to the driving shaft 10 in the vertical and horizontaldirections, respectively. In addition, the rotating shaft 2 a of themotor 2 can be positioned to the round hole 10 a of the driving shaft 10only by inserting the fillet into the square hole 21 b of the shaftcoupling 21.

FIG. 7 shows another embodiment of the shaft coupling. In the aboveembodiment, the shaft coupling 21 is fixed at the rotating shaft 2 a andthe driving shaft 10 a by the protruding part 21 c extending in theaxial direction and the fillet. In this embodiment, plural rigidityreducing holes 22 c extending in the radial direction of the shaftcoupling 22 are formed approximately at the axially symmetricalpositions. As the shaft coupling 22 is composed of resin material, theinner surface of the rigidity reducing hole 22 c is deformed plasticallyto the inward side when processing the rigidity reducing hole 22 c. Dueto this deformation, when inserting the rotating shaft 2 a into theround hole 22 a, the inner surface of the round hole 22 a is flared bythe rotating shaft 2 a and the firm engagement between the rotatingshaft 2 a and the shaft coupling 22 is established in thecircumferential direction without gap. On the side of the driving shaft10, the groove 22 b is formed so as to extend to the peripherycorresponding to the shape of the end part of the driving shaft 10.According to this way of forming the shaft coupling 22, the positioningbetween the motor shaft 2 a and the driving shaft 10 can be easilyestablished and the thermal deformation is treated in the similar way tothe above embodiment.

Now, referring to FIG. 3 and FIG. 5, the operation of the pump isdescribed. At the one position on the periphery of the driving shaft 10,the slotted surface 10 d is formed and the cross-section of the drivingshaft is shaped in a circle truncated with a straight line. As the hole(hole for the driving shaft) 11 a having the same cross-sectional shapeas the cross-section of the driving shaft at the slotted surface 10 d isformed at the eccentric shaft 11, the position of the eccentric shaft 11in the peripheral direction can be determined only by inserting thedriving shaft 10 into the hole 11 a for the driving shaft. When thedriving shaft 10 rotates, the rotation torque is transmitted from theslotted surface 10 d to the flat face 11 b of the hole 11 a for thedriving shaft, and then the eccentric shaft 11 rotates. In thisoperation, the axle center of the eccentric shaft 11 and the axle centerof the driving shaft 10 are not aligned to each other, the eccentricshaft 11 rotates in an eccentric motion.

In the above operation, due to the assembly error and gap between theeccentric shaft 11 and the driving shaft 10, the vibration gives rise tothe eccentric shaft 11 and the vibration amplitude may increase due tothe eccentric rotating motion of the eccentric shaft 11. As a result,the mechanical efficiency is reduced and the friction loss and abrasionat the sliding surface between the cylinder 4 and the piston 3 occur.Consequently, the abrasion and the thermal deformation cause thedecrease in the lifetime of the vacuum pump 1. In order to prevent thosedisadvantages, this embodiment uses the eccentric shaft 11 made of PPS(Polyphenylene Sulfide). By means of using the eccentric shaft 11 madeof PPS, as this material is lightweight and advantageous for abrasionresistance and heat resistance as well as relatively low abrasionresistance among other resin materials, the vacuum pump 1 can beoperated over the long term.

As the eccentric shaft 11 is lightweight, the unbalanced forcedistribution (centrifugal force) due to the eccentric rotating motioncan be reduced and thus the required mass of the balance weight 13 canbe reduced. Owing to this configuration, the downsizing of the vacuumpump can be achieved. Though this embodiment uses such a structure thatthe driving shaft 10 and the eccentric shaft 11 are engaged to eachother, it is allowed to apply the insert molding process to integrateboth parts. In case of insert molding, the driving shaft is positionedinside the die assembly and then the resin material for forming theeccentric shaft is filled in this die assembly. By means of forming theeccentric shaft 11 by the insert molding process, the alignment betweenthe eccentric shaft and the driving shaft 10 can be established, whichleads to increasing the performance of the compressor and reducing theman-hour cost for fabrication.

In contrast to the resin material used for the eccentric shaft, metallicmaterial which has an advantageous property in mechanical strength isused for the driving shaft 10. As the driving shaft 10 is made ofmetallic material, the coefficient of thermal expansion of the drivingshaft is different from the coefficient of the thermal expansion of theresin-made eccentric shaft 11. Due to the difference in theircoefficients of the thermal expansion, the eccentric shaft 11 tends totransform its shape in the peripheral direction to the driving shaft 10.In order to this problem, plural protruding parts 11 c is formed so asto extend in the axial direction on the flat face 11 b of the eccentricshaft 11. FIG. 8 shows the outline of the hole 11 a for the drivingshaft formed at the eccentric s haft 11. FIG. 8(a) is an outline of thehole 11 a for the driving shaft alone, and FIG. 8(b) is a cross-sectionview when inserting the driving shaft 10 into the hole 11 a.

In the similar manner to the case of the relation between the rotatingshaft 2 a of the motor 2 and the shaft coupling 21, when the drivingshaft 10 is inserted into the hole 11 a for the driving shaft, theprotruding part 11 c extending in the axial direction is deformedelastically or plastically, and then, the gap between the driving shaft10 and the eccentric shaft 11 goes out of existence. Then, even if thedriving shaft 10 and the eccentric shaft 11 yield to the heatdeformation due to the heat generated by the rotational movement of thedriving shaft 10, the steady state that the gap between he driving shaft10 and the eccentric shaft 11 does not exist can be maintained owing tothe deformation of the protruding part 11 b. Thus, the relativedisplacement of the eccentric shaft 11 in the circumferential directionrelative to the driving shaft 10 can be prevented.

In this embodiment, three protruding parts 11 c extending in the axialdirection are formed on the flat face 11 b with its cross-section shapedin D-sigmoid. In addition, as the length measured in the axial directionof the flat face 10 d of the driving shaft 10 ad the flat face 11 b ofthe eccentric shaft 10 is long, the flat faces 10 d and 11 b are madeslanted in the axial direction in view of easiness for assembly anddisassembly. The inclination angle in this slanted structure is about 1degree. As the vibration due to the existence of the gap between thedriving shaft 10 and the eccentric shaft 11 is reduced as in theabove-described way, the required mass for the balance weight 13 can bereduced.

A case study of applying the above-described small-sized vacuum pump 1to the automated urinary drainage system will be described below. Theentire component including the vacuum pump 1 is required to be replacedperiodically in view of sanitary supervision for the automated urinarydrainage system. In order to make the replacement parts recyclable, thecomponent of the vacuum pump 1 is so configured as to be enabled to bedisassembled material by material. Table 1 summarizes the analysis ofeasiness of assembly and disassembly and the preferable materials to beselected. TABLE 1 Performance Requirement (required feature marked with◯) Coefficient of Heat Expansion Material (marked Friction Coefficientselected in Light Heat with ◯ for Abrasion (marked with ◯ for UrinaryEasiness for the Part Symbol Weight Strength Resistance smaller values)Resistance larger values) Resistance Molding Process embodiment Driving10 ◯ ◯ Metal Shaft (Stainless) Shaft 21 ◯ ◯ PC/PCM Coupling Piston 3 ◯ ◯◯ ◯ ◯ ◯ PS/PC Eccentri 11 ◯ (Equivalent to ◯ ◯ PBT/PPS Shaft Piston) ◯Cylinder 4 ◯ (Equivalent to ◯ ◯ ◯ PBT Integrate Piston) ◯ with CasingSliding 7a, 7b ◯ (Larger than ◯ ◯ PPS/PBT Cylinder Piston) ◯ Flange 5(Equivalent to ◯ ◯ POM Piston) ◯ Cover 6 ◯ POM Motor 20 ◯ POM Base

As determined from the above reason, the materials used for the drivingshaft 10 and the eccentric shaft 11 are selected to be stainless steeland PBT/PPS, respectively. The material used for the piston 3 isselected to be PC/PC which has such advantageous chemical-resistantproperties as weak-acid resistance and weak-alkali resistance. Thosematerials have an advantageous mechanical deformation property.

The individual parts of the vacuum pump 1 expand due to heat in theoperation of the vacuum pump 1. The materials used for the cylinder 4,the eccentric shaft 11 and the sliding cylinders 7 a and 7 b for guidingthe blade part 3 a of the piston 3 are made approximately identical toone another in order to reduce the stress generated due to the thermalexpansion. In this embodiment, the material used for those parts isdetermined to PS (Polystyrene). In case of increasing the slidingperformance by installing the needle bearing 12 between the eccentricshaft 11 and the driving shaft 10, the needle bearing supporting part 3c for supporting the end face of the needle bearing 12 is formed at theeccentric shaft 11.

Corresponding to the position where the ball bearing 15 a and 15 b aresupported by the cylinder 4, the ball bearing positioning seats 11 g and11 h for pressing down in the axial direction to the inner face of theball bearing 15 a and 15 b are formed at the eccentric shaft 11. Thoseball bearing positioning seats 11 g and 11 h are shaped in a cylinder,and their length in the axial direction is about 0.5 mm. The size of theeccentric shaft 11 in the axial direction is almost the same as thewidth of the piston 3 and the pump room 4 b.

As for the material to be used for the cylinder, such a material thathas an advantageous property in abrasion resistance and heat resistanceand has weak-acid resistance and weak-alkali resistance and has amechanical property of easiness for molding should be selected. As thecylinder 4 slides with the piston 3, the material to be used for thecylinder 4 is selected to be PPS (Polyphenylene Sulfide) or PBT(Polybutylene Terphthalate) having approximately the same coefficient ofthermal expansion as the material of the piston 3. The material to beused for sliding cylinders 7 a and 7 b guiding the blade part 3 a of thepiston 3 is selected to be the material having an advantageous propertyin abrasion resistance and heat resistance and having approximately thesame coefficient of thermal expansion as the material of the piston 3.In this embodiment, also in view of easiness for molding process, PPS orPBT is used for the material of the sliding cylinders 7 a and 7 b.

The material to be used for the flange 5 is selected to be the materialhaving easiness for molding process, and having approximately the samecoefficient of thermal expansion as the material of the piston 3 and thecylinder 4. The material to be used for the flange requires a certainlevel of abrasion resistance which might not be less than the materialto be used for the other sliding parts. In this embodiment, the materialto be used for the flange is Homopolymer of POM (Polyacetal). In view ofeasiness for molding process, the material to be used for the motor base2 and cover 6 is selected to be Copolymer of POM.

The size of the vacuum pump is determined on the basis of the drainedurinary volume. By referring to the article in Acta Urologica Japonica,Vol. 33, No. 4, pp. 521-526, (April, 1987), which describes theinvestigation results of the urinary volumes for the individualgenerations (urinary volume per unit time), the drained urinary volumeof the adult people is estimated. According to this paper, the maximumdrained urinary volume of the young adult people between 19 to 39 yearsold is 28.2±4.6 mL per second, which is larger than the volume of anyother generation. The maximum drained urinary volume is determined to be40 mL per second on the safer side. By considering the involvement ofair and the other fluid dynamics loss, the overall drainage speed of thevacuum pump is determined to be 70 mL per second. Thus, assuming thatthe diameter of the cylinder is 17.2 mm, its length is 16.3 mm and thediameter of the piston is 14.0 mm, the drained volume per singlerevolution of the piston is approximately 1.066 mL, and the urine can bedrained by 76.4 mL per second by the vacuum pump 1 driven at 4300 rpm.Assuming that there exists approximately 10% loss, the urine can bedrained approximately by 70 mL per minute.

Though the sizes of the individual parts of the vacuum pump and itsrotating speed are determined as described above in this embodiment, itis allowed to select another sizes and rotating speed alternatively ifthe overall drain speed of 70 mL per second is attained. As thedownsizing and weight saving of the vacuum pump can be established sofar, the outline of the vacuum pump system integrated with the motor canbe determined so that the diameter may be 30 mm or shorter and itslength may be 70 mm or shorter. Owing to this configuration, it will beappreciated that the dry cell and the secondary battery, including solarcell and fuel cell, having the output voltage approximately from 4V to9V can be supplied as the electric power unit.

Although the present invention has been illustrated and described withrespect to exemplary embodiment thereof, it should be understood bythose skilled in the art that the foregoing and various other changes,omission and additions may be made therein and thereto, withoutdeparting from the spirit and scope of the present invention. Therefore,the present invention should not be understood as limited to thespecific embodiment set out above but to include all possibleembodiments which can be embodied within a scope encompassed andequivalent thereof with respect to the feature set out in the appendedclaims.

1. A hand-held vacuum pump formed by connecting an electric motor and amain body of vacuum pump formed with a pump room via a shaft coupling,wherein one bearing supporting a driving shaft of said main body ofvacuum pump is supported by a cylinder, and the other bearing issupported by a flange mounted hermetically at said cylinder; an end partof said cylinder at a side of an electric motor accommodates said shaftcoupling and is engaged with an end part of said electric motor; andsaid electric motor supports said cylinder.
 2. A hand-held vacuum pumpof claim 1, wherein a round hole engaged with a rotating shaft of saidelectric motor is formed at one side of said shaft coupling; aquasi-square hole engaged with a drive shaft penetrating inside saidcylinder is formed at the other side of said shaft coupling; and a holeengaged with a rotating shaft of said electric motor is formed at saiddriving shaft so that a locking screw for said shaft coupling and saidrotating shaft of said electric motor may not required.
 3. A hand-heldvacuum pump of claim 2, wherein an eccentric shaft made of resinmaterial aligned with an eccentric axis to said driving shaft and havingan outline cylindrical part is provided; a piston having an extensionpart configured as a plate structure at a part of periphery is mountedat an outer side of said eccentric shaft; and plural protruding partsextending in an axial direction of an inner face of said eccentric shaftare formed at an engaged part between said driving shaft and saideccentric shaft.
 4. A hand-held vacuum pump of claim 2, wherein amaterial to be used for said shaft coupling is selected to be a resinmaterial; and plural protruding parts extending in an axial direction atan inner face of a round hole formed said shaft coupling, or pluralprotruding parts extending in a radial direction and connecting to saidround hole.
 5. A hand-held vacuum pump wherein a couple of slidingcylinders clamping both sides of an intermediate part of an extensionpart of said plate structure and having a circular arc part is provided;said sliding cylinder is supported by a cylinder and said sidingcylinder is made oscillating inside said cylinder; said cylinder andsaid piston are formed as double cylinders; and a pump room is formed sothat a shape of said pump room may change between said double cylinders.6. An automated urinary drainage system having a hand-held vacuum pumpof one of claims 1 to 5, wherein an exhaust speed of said vacuum pump is70 mL/sec or larger, and a weight of said vacuum pump is 250 g orlighter.
 7. A hand-held vacuum pump of claim 1, wherein a piston ismounted at said driving shaft through an eccentric shaft; said pistonhas a blade part configured as a plate structure extending towards anouter side at a part of periphery; said sliding cylinder having acircular arc part supports said blade part so as to freely oscillate; amaterial of said driving shaft is made to be stainless steel, a materialof said shaft coupling is made to be PC resin or POM resin, a materialof said piston is made to be PS resin or PC resin, a material of thecylinder is made to be PBT resin, and a material of said slidingcylinder is made to be PPS resin or PBT resin, in which PC stands forPolycarbonade, POM stands for Polyacetal, PS stands for Polystyrene, PPSstands for Polyphenylene Sulfide, and PBT stands for PolybutyleneTerphthalate.
 8. A hand-held vacuum pump of claim 7, wherein a balanceweight is mounted at an end part of said driving shaft for compensatingan eccentricity between said piston and said eccentric shaft; a coverfor covering said balance weight is mounted at said flange; and amaterial of said flange is selected to be POM resin.
 9. A hand-heldvacuum pump of claim 7, wherein said cylinder and said piston are formedas double cylinders; and a gas inside a pump room is compressed bychanging a volume of said pump room formed between double cylinders byoscillating said blade part.
 10. A hand-held vacuum pump of claim 7,wherein a beveled cut part having a cross-sectional shape of shaftshaped in D-sigmoid is formed at said driving shaft; a holecorresponding to said D-sigmoid shape is formed at said eccentric shaft;and plural protruding parts extending in an axial direction inside saidhole shaped in D-sigmoid formed at an eccentric shaft.
 11. A hand-heldvacuum pump of claim 7, wherein a support part supporting said slidingcylinder is formed at said cylinder; a suction passage for sucking a gasinto said cylinder and a discharge passage for discharging a gas aremounted near said support part and a double cylinder part so as to bealmost vertical to a vibrating blade part; a valve configured in a sheetstructure for opening and closing said discharge passage and a dischargevalve presser for pressing down said valve are provided at saiddischarge passage.
 12. A hand-held vacuum pump of one of claims 7 to 11,wherein a diameter of said hand-held vacuum pump is 30 mm or shorter,its length is 70 mm or shorter, and its weight is 250 g or lighter; saidelectric motor is driven by a dry cell or a secondary battery providingan output voltage between 4V and 9V; and an overall exhaust velocitywhen driven by said vacuum pump at 4000 to 6000 rpm is about 80 mL/sec.